Collaborative Research: Investigating the Characteristics of Lower Tropospheric Airborne GPS Radio Occultation Observations and Their Impact in Hurricane Studies

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Project Summary The hurricane genesis process is known to depend on the degree of vertical instability needed to support deep convection and on mid-level moistening, which modulates convective activity. However, the time variation of moistening is poorly known due to the lack of high temporal and spatial observations during the genesis process. Global Positioning System (GPS) Radio Occultation (RO) provides area-averaged profiles of refractivity (which depends on moisture and temperature) with very high vertical resolutions that are complementary to dropsondes (pointwise, high vertical resolution) and satellite retrievals (high horizontal but poor vertical resolution). GPS RO is insensitive to heavy precipitation, clouds, and winds. Since the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) became operational, space borne GPS RO data have shown a positive impact on global numerical weather prediction models in the mid to upper troposphere range. However, the use of the data at lower levels has lagged for several reasons: 1) complications due to strong horizontal variations in moisture 2) difficulties in signal tracking and 3) sparse observations within the window of interest for mesoscale systems. This has led to minimal impact in tropical cyclone genesis and forecasting, and minimal impact below mid-troposphere in general. Airborne RO can play a major role in advancing understanding of the hurricane genesis process, because dense targeted measurements are simpler to make with an airborne system than with the existing space borne constellation. The PIs will take advantage of a unique opportunity to collect data during the Pre-Depression Investigation of Cloud Systems of the Tropics (PREDICT) campaign in August 2010, which will allow them to test their progress in data assimilation for the case of tropical cyclone genesis. The data assimilation results should be of great interest to PREDICT investigators because they will provide better initial conditions for high-resolution models for testing new hypotheses concerning the evolution of tropical disturbances into hurricanes. Broader Impacts: The project will promote the use of airborne radio occultation to an expanded research community and serve as a feasibility test for hurricane hunter surveillance missions, potentially resulting in a direct societal benefit from improved operational forecasts. This research activity will educate graduate students and promote the advancement of postdoctoral researchers within an international collaborative structure between Taiwan and US universities. It will strengthen research programs led by four female investigators, who will serve as role models for their students as well as other young female scientists.